Cancer a disease in which a group of cells display the traits of uncontrolled growth. This means that the cells grow and divide beyond the levels of normal limits. The cells are also able to invade and destroy surrounding tissues. In addition cancer cells sometimes also metastasize, meaning that they spread to other locations in the body via the blood or lymph.
Most cancers are caused by abnormalities in the genetic material of the cells. These abnormalities may be due to the effects of carcinogens. Other cancer-promoting genetic abnormalities may be randomly acquired through errors in DNA replication, or are inherited, and thus present in all cells from birth.
Genetic abnormalities found in cancer typically affect two general classes of genes. Cancer-promoting oncogenes are often activated in cancer cells, giving those cells new properties, such as hyperactive growth and division, protection against programmed cell death, loss of respect for normal tissue boundaries, and the ability to become established in diverse tissue environments.
Tumour suppressor genes are often inactivated in cancer cells, resulting in the loss of normal functions in those cells, such as accurate DNA replication, control over the cell cycle, orientation and adhesion within tissues, and interaction with protective cells of the immune system.
There are many different types of cancer and the cancer is usually classified according to the type of tissue from which it originated.
Cancer is usually treated by one or more of the following: surgery, chemotherapy, radiation therapy, immunotherapy and monoclonal antibody therapy. The type of therapy depends upon the location and grade of the tumour and the stage of the disease.
Complete removal of the cancer without damage to the rest of the body is the goal of treatment. Sometimes this can be accomplished by surgery, but the propensity of cancers to invade adjacent tissue or to spread to distant sites by microscopic metastasis often limits its effectiveness. The effectiveness of chemotherapy is often limited by toxicity to other tissues in the body. Radiation can also cause damage to normal tissue.
Cancers are known to affect many areas of the body with the most common types of cancers including: cancer of the bile duct, cancer of the bladder, cancer of the bone, cancer of the bowel (including cancer of the colon and cancer of the rectum), cancer of the brain, cancer of the breast, cancer of the neuroendocrine system (commonly known as a carcinoid), cancer of the cervix, cancer of the eye, cancer of the oesophagus, cancer of the head and neck (this group includes carcinomas that start in the cells that form the lining of the mouth, nose, throat, ear or the surface layer covering the tongue), Kaposi's sarcoma, cancer of the kidney, cancer of the larynx, leukaemia, cancer of the liver, cancer of the lung, cancer of the lymph nodes, Hodgkin's lymphoma, non-Hodgkin's lymphoma, melanoma, mesothelioma, myeloma, cancer of the ovary, cancer of the pancreas, cancer of the penis, cancer of the prostate, skin cancer, soft tissue sarcomas, cancer of the spinal cord, cancer of the stomach, testicular cancer, cancer of the thyroid, cancer of the vagina, cancer of the vulva and cancer of the uterus.
A tumour that develops in the brain can destroy or damage brain cells by producing inflammation, compressing other parts of the brain, inducing cerebral oedema (brain swelling) and can cause increases in intracranial pressure (pressure within the skull).
Each year, approximately 4300 people in the UK are diagnosed with a brain tumour. A primary brain tumour is a mass created by the growth or uncontrolled proliferation of cells in the brain. Malignant primary brain tumours are most likely to cause problems by spreading into the normal brain tissue which surrounds them and causing pressure and damage to the surrounding areas of the brain. These tumours rarely spread outside the brain to other parts of the body. However, secondary brain tumours occur when cancer cells from other parts of the body, such as the lung or breast spread to the brain.
Surgery is the treatment option of choice for many brain tumours. Some may be completely excised, but those that are deep or that infiltrate brain tissue may be debulked rather than removed.
Radiation therapy and chemotherapy may be recommended depending on the type of tumour involved.
Glioma cell tumours can often be lethal. The characteristic diffuse infiltrative tumour growth of gliomas often makes the surgical removal of them impossible and this profoundly complicates the clinical management of these patients.
Glioblastoma multiforme (GBM) is the most common and most aggressive type of primary brain tumour and accounts for 52% of all primary brain tumour cases and 20% of all intracranial tumours.
Different approaches are being researched in order to improve the mortality rate of patients diagnosed with a glioma. These include therapies that target the glioma cells but leave normal cells unharmed, methods that limit the spread of the cancer cells and treatments that block the tumours life-sustaining molecules.
One such area of research involves the use of cannabinoids as anti-tumoural agents.
Cannabinoids are the active constituents of cannabis plants and they have been found to demonstrate numerous pharmacological properties.
For example EP1177790 (Guzman et al.) describes the treatment of cerebral tumours by the administration of a natural or synthetic cannabinoid, specifically THC. It is claimed that activation of specific receptors leads to selective death of the transformed cells.
Recently the cannabinoid CBD has been shown to possess anti-tumoural properties (Massi et al. 2004). The work described by this paper describes anti-proliferative effects both in-vitro using U87 and U373 human glioma cell lines and in-vivo using U87 human glioma cells subcutaneously implanted to nude mice.
Malignant gliomas are highly infiltrative and proliferative tumours, which follow a characteristic pattern of growth. Glioma cells invade the adjacent normal brain structures and surrounding large blood vessels.
In addition the applicant's earlier patent EP1802274 describes the use of the cannabinoid CBD to impede the progress of cancer cells migrating from their primary tumour location to a secondary site.
Furthermore, Medical hypothesis (2006) vol 66, pages 234-246 discusses the physiological and clinical effects of THC and CBD and presents a rationale for their combination. Under “neoplastic disease” (page 242) it is acknowledged that THC has cytotoxic benefits and that CBD has also proven cytostatic/cytotoxic. It is suggested, given the analgesic effects of the CBD:THC combination in cancer treatment, the side benefit of THC and CBD in chemotherapy induced nausea, and these primary effects on tumor growth and spread that there is a strong rational for additional clinical trials. However, the generality of this teaching could not have predicted the benefits that could be achieve in combination in what would otherwise have been considered sub-optimal (or ineffective amounts) for the compounds alone.